Fe2(SO4)3-assisted anaerobic digestion of pig manure: the performance of biogas yield and heavy metal passivation

Abstract

Abstract The harmless disposal and recycling treatment technology of livestock manure has received increasing attention in recent years. In this study, Fe2(SO4)3 was added during anaerobic digestion (AD) of pig manure (PM) to investigate the effects of different doses of Fe2(SO4)3 on biogas yield and heavy metal passivation. The results showed that the highest biogas yield was observed after adding a moderate dose of Fe2(SO4)3 (3%, based on the total solids), while the elevated result was inhibited as the Fe2(SO4)3 dosage increased. The analysis of solid digestate (solid matter remaining after AD) revealed that AD effectively passivated Cu, Zn, and As, which can be further improved with the addition of Fe2(SO4)3. However, the passivated Cd performance during this process was negligible. Furthermore, seed germination index (GI) trial results indicated that Fe2(SO4)3-assisted AD reduced the toxicity of end products to plants. To summarize, AD assisted by the addition of an appropriate amount of Fe2(SO4)3 is feasible to treat PM, and the addition of Fe2(SO4)3 at 3% was the most economic and environmental-friendly. This work could provide useful methods for the control of heavy metal pollution in the soil. Article highlights Adding 3% dose of Fe2(SO4)3 could increase methane yield by 66.76%. Fe2(SO4)3-assisted AD passivated HMs and reduced their bioavailability. The 3% Fe2(SO4)3-assisted AD significantly reduced the toxicity of end products to plants.